Pfizer/Medivation Dimebon fails as Huntington disease drug

Pfizer and Medivation's Dimebon, which failed as a potential treatment for Alzheimer's last year, has now disappointed in a late-stage trial for Huntington disease.

The companies have presented results from the 403-patient Phase III HORIZON study of Dimebon (latrepirdine) which show that the drug did not achieve statistical significance for either of the co-primary endpoints of the trial. Full results are expected to be presented at an upcoming medical meeting.

David Hung, Medivation's chief executive, said "we are disappointed with the results of the HORIZON trial given the high unmet need in this patient population". He added that "at this point, we will discontinue development of Dimebon in Huntington disease, including the ongoing open-label extension study".

However this may not be the end of the road for Dimebon, which was first sold in Russia as an antihistamine. Dr Hung noted that the firms will continue a 12-month Phase III trial looking at the benefit of adding Dimebon to Eisai/Pfizer's Aricept (donepezil) in patients with mild-to-moderate Alzheimer's disease. Top-line data from that study is expected in the first half of 2012.

Last March, Dimebon failed in an Alzheimer's trial where no statistically significant improvements were achieved on cognition, global function, activities of daily living or behaviour.

Pfizer linked up with Medivation in September 2008 in a deal which saw the latter pocket an upfront cash fee of $225 million with milestone payments of up to $500 million, depending on the success of Dimebon.